FLSC Message Board: Saturday ?

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Saturday ?

Posted by Ray on 8/29/2009, 7:32 am
69.205.81.50

OK so I goofed up the name...but not the physics. Danny, not Dave, has been pumping water vapor up and into the approaching low for days. Water vapor, when it condenses, is the primary energy source for thunderstorms, tornadoes, and hurricanes. Storms are rated by their top winds. That is the easiest, but not the most meaningful, way to rate them. To wit: you can have a small storm with top winds of 200 mph, or a storm with three times the horizontal extent (i.e. 9 times the area), with winds of 150 mph. The first, although given a higher category, would have much less total energy, both kinetic (wind) and potential (water vapor). And consequently, much less influence on the general atmospheric circulation. But it takes a lot more work, and cost, to integrate those variables over a large storm. Hourly rate for a Lockheed WP-3D Orion isn't peanuts.

Yup, Danny's still a player. Check this out, from the Gloucester Daily Times, posted 2:18 this AM:
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Last week's offshore visit from Hurricane Bill was benign. While Bill churned up substantial surf up and down the coast, its most memorable calling card for Gloucester and Cape Ann may have come last Sunday afternoon, when that surf covered virtually all of Good Harbor Beach.

Today's meeting with Tropical Storm Danny, however, is expected to be more serious. A gale watch is in effect through tonight, and, as of last night, forecasts were calling for Danny-driven winds of 20 to 25 knots, with gusts up to 35 knots tonight. Forecasters were also predicting up to two inches of rain as the downgraded hurricane passes off the coast, with showers tonight and into tomorrow morning.
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So, what about today?, about which I said nothing yesterday. Because, both are still up in the air, literally. The sub-synoptic scale spokes of energy which rotate around synoptic-scale systems, which bring precip, and between which are "dry slots", are a b###h to pin down.

You want confusion? Check out this for today from NWS Buffalo (posted 7:54 PM yesterday, not yet updated...they must still be in bed):

FURTHER TO THE WEST...EXPECT THE NIAGARA FRONTIER...SOUTHERN TIER...AND GENESEE VALLEY TO POSSIBLY SEE TWO OR THREE ROUNDS OF PRECIPITATION GENERALLY MOVING IN FROM THE WEST. THE LAST ONE...WITH/AHEAD OF THE COLD FRONT AND DEEPENING SURFACE LOW...SHOULD BE THE ONE THAT PRODUCES THE MOST PRECIPITATION...BUT DO NOT EXPECT AS MUCH OVERALL PRECIPITATION COMPARED TO AREAS TO THE EAST.

And then compare with this for Sunday, same source:

..ONE OTHER THING WE WILL NEED TO BE ON THE LOOKOUT FOR IS THE POTENTIAL FOR SOME LAKE ENHANCED/LAKE EFFECT RAIN SHOWERS TO DEVELOP TO THE LEE OF THE LAKES FROM THE SECOND HALF OF SATURDAY NIGHT INTO SUNDAY NIGHT...WHEN THERE WILL BE ENOUGH LOW LEVEL MOISTURE TO SUPPORT SUCH ACTIVITY. THE INITIAL PREVAILING WEST-SOUTHWESTERLY FLOW WOULD SUPPORT THE POTENTIAL FOR LAKE EFFECT/ENHANCED TO DEVELOP EAST-NORTHEAST OF BOTH LAKES LATER SATURDAY NIGHT...BEFORE ANY SUCH ACTIVITY DROPS SOUTHWARD AND FALLING APART DURING SUNDAY MORNING AS THE FLOW BECOMES MORE WESTERLY...AND STRONG LATE SUMMER DIURNAL INFLUENCES COME INTO PLAY. AFTER MORE GENERAL DIURNALLY-DRIVEN CONVECTION SUNDAY AFTERNOON...SOME LIMITED ACTIVITY MAY THEN REDEVELOP SOUTHEAST OF THE LAKES ON A NORTHWESTERLY FLOW SUNDAY NIGHT...BEFORE FIZZLING OUT BY MONDAY MORNING AS THE FLOW BECOMES MORE NORTHERLY...

Yesterday I was optimistic about Sunday. The latest comparison of the 36 hour GFS and NAM 500 mb vorticity plots (much more accurate that the 72 hour) shows that they have now converged nicely (although that's no guarantee either) on a solution for tomorrow morning: a wicked swath of positive vorticity (= bad) right over western NY. Go figure.

Alzeimer's....relentless.

Ray